How do Organisms Reproduce?: Class 10 Science Q&A · Page 5
112 free answers on How do Organisms Reproduce? (Science) for Class 10 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- ScienceClass 10CBSE
1. Which of the following statements is not true with respect to variation? (a) All variations in a species have an equal chance of survival (b) Change in genetic composition results in variation (c) Selection of variants by environmental factors forms the basis of evolutionary processes Variation is minimum in asexual reproduction
Soln: The answer is (a) All variations in a species have an equal chance of survival Explanation Statement a) is wrong because only useful variations have a chance of survival. Nature chooses the fittest variation to survive.
- ScienceClass 10CBSE
1. If the fossil of an organism is found in the deeper layers of the earth, then we can predict that (a) the extinction of the organism occurred recently (b) the extinction of the organism occurred thousands of years ago (c) the fossil position in the layers of the earth is not related to its time of extinction time of extinction cannot be determined
Soln: The answer is (b) the extinction of the organism occurred thousands of years ago Explanation: Older fossils are found deep in the earth. Hence option b) is the right answer.
- ScienceClass 10CBSE
1. Select the correct statement (a) Tendril of a pea plant and phylloclade of Opuntia are homologous (b) Tendril of a pea plant and phylloclade of Opuntia are analogous (c) Wings of birds and limbs of lizards are analogous Wings of birds and wings of bats are homologous
Soln: The answer is (a) Tendril of a pea plant and phylloclade of Opuntia are homologous Explanation: Homologous structures share a common origin but may have evolved to perform similar or different functions. Tendrils in the pea plant are modified leaves that help in climbing, whereas the phylloclade of Opuntia is a flattened stem with leaves modified into spines to reduce transpiration. Since, tendrils and spines share
- ScienceClass 10CBSE
1. A basket of vegetables contains carrot, potato, radish and tomato. Which of them represents the correct homologous structures? (a) Carrot and potato (b) Carrot and tomato (c) Radish and carrot (d) Radish and potato Soln:
The answer is (c) Radish and carrot Explanation: Homologous structures have a common origin. Among the given options, carrot and radish are the modified roots that store food, potato is a modified stem and tomato is a fruit. Hence, carrot and radish are examples of homologous structures.
- ScienceClass 10CBSE
1. Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds, produce F1 progeny that has round, yellow (RrYy) seeds. When F1 plants are selfed, the F2 progeny will have a new combination of characters. Choose the new combination from the following. (i) Round, yellow (ii) Round, green (iii) Wrinkled, yellow (iv) Wrinkled, green (a) (i) and (ii) (b) (i) and (iv) (c) (ii) and (iii) (d) (i) and (iii)
Soln: The answer is The new combinations in F2 progenies will be round yellow and wrinkled green. When F1 progeny that has round yellow (RrYy) seeds is selfed, we get the phenotypic ratio of 9:3:3:1 for round yellow, round green, wrinkled yellow and wrinkled green seeds in the F2 generation.
- ScienceClass 10CBSE
1. New species may be formed if (i) DNA undergoes significant changes in germ cells (ii) chromosome number changes in the gamete (iii) there is no change in the genetic material (iv) mating does not take place (a) (i) and (ii) (b) (i) and (iii) (c) (ii), (iii) and (iv) (i), (ii) and (iii)
Soln: The answer is (a) (i) and (ii) Explanation: Evolution will not take place without change and variation in the genetic material. Hence, the change in genetic material and variation in chromosomes are required for the evolution of new species.
- ScienceClass 10CBSE
1. Select the incorrect statement. (a) Frequency of certain genes in a population changes over several generations resulting in evolution (b) Reduction in weight of the organism due to starvation is genetically controlled (c) Low-weight parents can have heavyweight progeny Traits which are not inherited over generations do not cause evolution
Soln: The answer is (b) Reduction in weight of the organism due to starvation is genetically controlled Explanation: Option b) is a wrong statement because weight loss and gain are controlled by external factors, and they are not controlled genetically.
- ScienceClass 10CBSE
1. A zygote which has an X-chromosome inherited from the father will develop into a (a) boy (b) girl (c) X- chromosome does not determine the sex of a child either boy or girl
Soln: The answer is (b) girl Explanation: If sperm with the Y chromosome fertilises the egg, the zygote will develop into a male child. If sperm with an X chromosome fertilises the egg, the zygote will develop into a female child.
- ScienceClass 10CBSE
1. The maleness of a child is determined by (a) the X chromosome in the zygote (b) the Y chromosome in the zygote (c) the cytoplasm of the germ cell, which determines the sex sex is determined by chance
Soln: The answer is (b) the Y chromosome in the zygote Explanation: If sperm with a Y chromosome fertilises the egg, the zygote will develop into a male child. If sperm with an X chromosome fertilises the egg, the zygote will develop into a female child.
- ScienceClass 10CBSE
1. In human males, all the chromosomes are paired perfectly except one. This/these unpaired chromosome/s is/are (i) large chromosome (ii) small chromosome (iii) Y-chromosome (iv) X-chromosome (a) (i) and (ii) (b) (iii) only (c) (iii) and (iv) (ii) and (iv)
Soln: The answer is (c) (iii) and (iv) Explanation: Humans have 22 pairs of autosomes and a sex chromosome. Autosomes make perfect pair. Sex chromosomes, arenot always a perfect pair. Women have a perfect pair of sex chromosomes, i.e. XX. But men have a mismatched pair, i.e. XY in which X is a normal-sized X while Y is short.
- ScienceClass 10CBSE
1. Which of the following statements is incorrect? (a) For every hormone, there is a gene. (b) For every protein, there is a gene. (c) For the production of every enzyme, there is a gene. For every molecule of fat, there is a gene
Soln: The answer is (d) for every molecule of fat, there is a gene Explanation: Every protein, enzyme and hormone is controlled by a specific gene, whereas fats are not controlled by a gene; hence, option d is a wrong statement.
- ScienceClass 10CBSE
1. A cross between a tall plant (TT) and a short pea plant (tt) resulted in progeny that was all tall plants because (a) tallness is the dominant trait (b) shortness is the dominant trait (c) tallness is the recessive trait (d) height of the pea plant is not governed by gene ‘T’ or ‘t’
The answer is (a) tallness is the dominant trait Explanation: A cross between a tall plant (TT) and a short pea plant (tt) results in the progeny that is all tall plants but with Tt genotype. In the heterozygous plants the dominant trait is expressed phenotypically. Single copy of the ‘T’ is enough to make the plant tall.
- ScienceClass 10CBSE
1. Two pink-coloured flowers on the crossing resulted in 1 red, 2 pink and 1 white flower progeny. The nature of the cross will be (a) double fertilisation (b) self-pollination (c) cross-fertilisation no fertilisation
Soln: The answer is (b) self-pollination
- ScienceClass 10CBSE
1. Exchange of genetic material takes place in (a) vegetative reproduction (b) asexual reproduction (c) sexual reproduction budding
Soln: The answer is (c) sexual reproduction Explanation: Apart from sexual reproduction, other options are a type of asexual reproduction where only a single parent is involved. Hence, the correct answer is sexual reproduction, where exchange of genetic material takes place.
- ScienceClass 10CBSE
How does reproduction help in providing stability to populations of species?
Solution: Reproduction is the process of producing the same kind of species by the existing species. This is done so as to maintain the population of that species and also to take forward their species to the next generations. Stability is maintained by keeping a check of rate of births and rate of deaths.
- ScienceClass 10CBSE
How are the modes for reproduction different in unicellular and multicellular organisms?
Solution: The different modes of reproduction in unicellular organisms are fission, budding, etc. Here, the cell divides into two daughter cells and this process of cell division continues. Whereas, in multicellular organisms there is a different organ system for reproduction. The different modes of reproduction in multicellular organisms are vegetative propagation, spore formation, etc. In more complex organisms like humans and animals, reproduction i
- ScienceClass 10CBSE
What are the different methods of contraception?
Solution: Following are the different methods of contraception: Natural method: In this method, the main focus is to avoid the meeting of sperms and ovum. This can be achieved by avoiding the mating from 10th to 17th day of the menstrual cycle. During this period, there are high chances of fertilization as ovulation is expected. Barrier method: In this method, the meeting of sperms and ovum is avoided by using a
- ScienceClass 10CBSE
Why does menstruation occur?
Solution: Menstruation is the normal bleeding of the vaginal line, which starts at puberty and lasts till menopause. During this period, the body prepares itself for pregnancy. Every month an egg is released from one of the ovaries at the same time when the uterus prepares itself for the fertilized egg. The inner lining of the uterus gets thickened and is supplied with a sufficient amount of blood for the embryo. Since there is no interaction between the egg a
- ScienceClass 10CBSE
What are the functions performed by the testis in human beings?
Solution: Following are the functions performed by the testis in human beings: Apart from the production of sperms, it also produces the male hormone known as androgens. They also produce hormone called testosterone, which is responsible for secondary sexual characters in boys.
- ScienceClass 10CBSE
The anther contains (a) Sepals (b) Ovules (c) Pistil (d) Pollen grains
Solution: (d) Pollen grains. Pollen grains are the microscopic particles that occurs in the pollen giving rise to male gametophyte of a seed plant.